Accumulated Other Comprehensive Loss - Reclassifications (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Reclassifications out of accumulated other comprehensive income loss by component
Other income (expense), net	$ (5)	$ 21
Total before tax	(6,027)	236
Income tax benefit	(138)	(121)
Net (loss) income	(6,165)	115
Decrease (Increase) in Net Income | Net actuarial loss
Reclassifications out of accumulated other comprehensive income loss by component
Other income (expense), net	57	44
Decrease (Increase) in Net Income | Prior service cost
Reclassifications out of accumulated other comprehensive income loss by component
Other income (expense), net	2	3
Decrease (Increase) in Net Income | Defined benefit plan
Reclassifications out of accumulated other comprehensive income loss by component
Total before tax	59	47
Income tax benefit	(15)	(12)
Net (loss) income	$ 44	$ 35